Dimerization of diolefinic compounds

ABSTRACT

Conjugated diolefinic hydrocarbons are dimerized in the presence of certain organopalladium complex catalytic compositions of matter at dimerization conditions to produce a selective dimer of a starting material.

United States Patent De Young 1 Sept. 12, 1972 [54] DIMERIZATION OFDIOLEFINIC 3,522,321 7/1970 DeYoung ..260/666 COMPOUNDS 3,501,540 3/1970 Zuech ..260/666 Inventor: Edwin L. De Young, Chicago, 1. 2,707,1964/1955 Woods ..260/638 [73] Assignee: Universal Oil Products Company,Primary EXami"r-De1bert E n l Des Plaines, Ill. Assistant Examiner-J.Nelson Attorney-James R. l-loatson, Jr. and Raymond H. [22] Filed: Oct.7, 1970 Nelson [21] App]. No.: 78,951 ABSTRACT Conjugated diolefinichydrocarbons are dimerized in [52] US. Cl ..260/677 R, 260/666 B thepresence of certain organopanadium complex [51] Illl. Cl ..C07c 11/24catalytic compositions of matter at dimerization com [58] Field ofSearch ..260/677, 666 B ditions to produce a selective dimer of astarting material. [56] References Cited UNITED STATES PATENTS 5/1969Kohnle et al. ..260/677 9 Claims, No Drawings DIMERIZATION OF DIOLEFINICCOMPOUNDS This invention relates to a process for the dimerization ofunsaturated compounds and particularly, the invention is concerned withthe process for dimerizing a diolefinic hydrocarbon to produce compoundswhich are useful as aroma chemicals.

Heretofore, many aroma compositions, such as perfumes, have depended, toa great extent, upon naturally occurring compounds which are blended orformulated to prepare final compositions of matter which have a pleasingand pleasant fragrance. For example, perfumes which comprise a mixtureof organic compounds which include, for example, alcohols, aldehydes,ketones, esters, and hydrocarbons, are all combined in fixed proportionso that the odors of the fixed compounds will combine to produce aharmonious fragrance. Some of these compounds which are blended havebeen prepared from rose petals, geranium petals, or other flower petalswhich possess a distinctive fragrance; and thus, the product thereof isdependent on nature as pertains to the growing season, the harvesting ofthe crops, as well as climatic conditions which will insure either anabundant crop or may in some instances, insure a poor or sparse crop ofthe desired flower. Therefore, in order to insure a continued andcertain supply of various aromas, it is necessary to synthesize thecompounds which possess the desired odor. By utilizing these syntheticcompounds in place of the naturally occurring compounds, it is possibleto prepare aroma chemicals such as geraniol, linalool, geranyl chloride,linalyl chloride, geranyl acetate, linalyl acetate, etc., which may beused in formulations thereafter used in the perfume and soap industryfor preparing the formulations which are used to scent soaps,detergents, talcums, perfumes, colognes, etc.

In this respect, it has now been discovered that certain hydrocarbons,and particularly a diolefinic hydrocarbon such as isoprene, may betreated in the presence of certain catalysts of the type hereinafter setforth in greater detail to prepare novel compositions of matter whichpossess distinctive, desirable, and pleasing odors.

it is therefore an object of this invention to prepare novelcompositions of matter hereinafter set forth in greater detail.

A further object of this invention is to provide a process for effectingthe polymerization and particularly the dimerization of certaindiolefinic hydrocarbons to prepare novel compositions of matter usefulin the fragrance field.

In one aspect an embodiment of this invention resides in a process forthe selective dimerization of a conjugated diolefinic hydrocarbon whichcomprises treating said hydrocarbon at dimerization conditions in thepresence of an organopalladium complex, and recovering the resultantdimer.

A specific embodiment of this invention is found in a process for thedimerization of isoprene which com prises treating isoprene at atemperature in the range of from about 25 to about 250C. and at apressure in the range of from about atmospheric to about 100 atmospheresin the presence of a catalyst consisting oftetrakis(triphenylphosphite)-palladium(), and recovering the resultant2,7-dimethyl-l ,3 ,7-octatriene.

Other objects and embodiments will be found in the following furtherdetailed description of the present invention.

It has now been discovered that selective dimerization of unsaturatedcompounds, and particularly diolefinic hydrocarbons may be effected inthe presence of certain catalytic compositions of matter underdimerization conditions. These dimerization conditions will includetemperatures ranging from ambient (25C.)up to about 250C. or more and ata pressure in the range of from about atmospheric to about atmospheres,or more. When utilizing superatmospheric pressure, the desired pressuremay be provided for by the introduction of a substantially inert gassuch as nitrogen into the reaction vessel, the amount of pressure whichis utilized by that which is necessary to maintain a major portion ofthe reactant in the liquid phase. The reaction time duringwhich'the'dimerization of the diolefinic hydrocarbon is effected mayrange from about 0.5 up to about 24 hours or more in reaction thedesired residence time which is required to effect the dimerizationbeing dependent upon a number of variable conditions or factors amongwhich will include the particular diolefinic hydrocarbon, the reactiontemperature and the reaction pressure, etc.

The catalytic composition of matter which is utilized to effectthedimerization of the diolefinic hydrocarbon will comprise anorganopalladium complex. Specific examples of these organopalladiumcatalysts will include tetrakis(triphenylphosphite)palladium(0),tetrakis(tribenzyl phosphite)palladium(0),tetrakis(tritolylphosphite)palladium(0),

tetrakis( triethylbenzylphosphite )'palladium( 0tetrakis(trixylylphosphite )-palladium(0), etc. It is to be understoodthat the aforementioned organopalladium complexes are onlyrepresentative of the type of catalyst compositions which may be used,and that the present invention is not necessarily limited thereto.

As hereinbefore set forth, the utilization of the particular catalyticcomposition of matter will permit a selective dimerization of thediolefinic hydrocarbon. For example, when dimerizing a branched chaindiolefinic hydrocarbon, it has been found that the dimerization will beeffected in a manner whereby a greater proportion of a tail to taildimer will be ob tained rather than that proportion which is obtained ina random head to head, head to tail, or tail to tail dimerization.Examples of unsaturated compounds, and particularly diolefinichydrocarbons, which may undergo dimerizationacco'rding'to the process ofthis invention will include straight chain diolefins such as1,3-butadiene, l,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene,1,3-heptadiene, 2,4-heptadiene, etc., branched chain diolefinichydrocarbons such as 2'-methyl-l ,3-butadiene (isoprene),2,3-dimethyl-l,3-butadiene, 2- methyl- 1 ,3-pentadiene,3-methyl-l,B-pentadiene, 2 ,3- dimethyl-l ,3-pentadiene, Z-methyl-l ,3-hexadiene,3- methyl-l,3-'hexadiene, 2-methyl-2,4-hexadiene, 2- methyll,3heptadiene,3-methyl-l ,3-heptadiene, 2- methy l.-2,4-heptadiene,3-methyl-2,4-heptadiene, 2- methyl-l,3-octadiene,Z-methyI-Z'J-octadiene, 3- methyl-2,7-octadiene,2-methyl-6-methylene-2,7-octadiene (myrcene), etc. It is to beunderstood that the aforementioned diolefinic hydrocarbons are onlyrepresentative of the class of compounds which may be subjected to aselective dimerization reaction, and that the present invention is notnecessarily limited thereto.

The process of this invention in which the diolefinic hydrocarbon issubjected to dimerization in the presence of certain catalysts may beeffected in any suitable manner and may comprise either a batch orcontinuous type operation. For example, when a batch type operation isused, the particular diolefinic hydrocarbon such as isoprene is placedin an appropriate apparatus, the particular reaction vessel beingdependent upon whether or not superatmospheric pressures are to be usedto effect the reaction. For example when utilizing a reaction which isto be effected at superatmospheric pressure, the diolefinic hydrocarbonis charged to an autoclave which may be of the rotating or mixing typeand which contains the organopalladium catalyst of the type hereinbeforeset forth in greater detail. The vessel is sealed, nitrogen is pressedin until the desired operating pressure has been reached and thereaction vessel is then heated to the desired temperature. Uponcompletion of the predetermined residence time, the autoclave andcontents thereof are allowed to return to room temperature, the excesspressure is discharged and the reaction mixture is recovered. Thereaction mixture is then separated from the catalyst and subjected toconventional means of separation and recovery whereby the desired dimerwhich possess the particular configuration such as, as hereinbefore setforth, a tail to tail linkage may be recovered. The conventional meansof separation and recovery which may be employed will include washing,drying, extraction, fractional distillation, etc., whereby the desiredcuts are separated from another unreacted starting material and/or sideproduct which may have been formed during the reaction.

It is also contemplated within the scope of this invention that theprocess to effect a selective dimerization of the diolefinic hydrocarbonmay be effected in a continuous manner of operation. For example, oneparticular type of continuous type of operation which may be effectedcomprises the fixed bed operation in which the catalyst is disclosed asa fixed bed in a reaction zone which is maintained at the properoperating conditions of temperature and pressure. The particulardiolefinic hydrocarbon such as isoprene which is to undergo dimerizationis continuously charged to the reaction zone and passed through thefixed bed of the catalyst in either an upward or downward flow. Uponcompletion of the desired residence time, the reactor effluent iscontinuously withdrawn from the reactor and subjected to separation fromthe type hereinbefore set forth in greater detail whereby the selectivedimers possessing a tail to tail linkage are separated and recoveredfrom any unwanted dimer, said reaction products which may have beenformed and unreacted diolefinic hydrocarbons, the latter being recycledto form a portion of the feed stock. Another type of continuous typeoperation which may be used comprises the moving bed type operation inwhich the catalyst and the diolefinic hydrocarbon such as isoprene arepassed through the reaction Zone which is maintained at the properoperating conditions of temperature and pressure either concurrently orcountercurrently to each other. Yet another type of operation which maybe used comprises the slurry type of operation in which the catalyst iscarried into the reaction zone as a slurry with the diolefinichydrocarbon. in the latter two types of ope ration the reactor effluentis also continuously withdrawn from the reaction zone and treated in amanner similar to that described for the treatment of the reactoreffluent in the fixed bed type of operation, the desired dimercontaining a specific configuration being recovered while the unreacteddiolefinic hydrocarbon is recycled to form a portion of the feed stock.

The following examples are given to illustrate the process of thepresent invention which, however, are not intended to limit thegenerally broad scope of the present invention in strict accordancetherewith.

EXAMPLE I The catalyst complex which is utilized for the dimerization ofisoprene was prepared by adding 15.5 g. (0.05 mol) of triphenylphosphiteto a hot, nitrogen purged, solution of 1.7 g. (0.01 mol) of palladiumchloride in 100 cc. of acetonitrile, followed by the dropwise additionof 5 cc. of diethylamine. The solution was cooled under a nitrogenblanket and the resulting crystals were filtered under a suction of anitrogen purged container. The product was recrystalized from 250 cc. ofhot nitrogen purged absolute ethyl alcohol, said product forming aswhite plates which had a melting point of 123 -l27 C. and comprisetetrakis(triphenylphosphite)palladium(0).

Following this, 5] g. (0.75 mol) ofisoprene and 1.25 g. (0.00093 mol) oftetrakis(triphenylphosphite)palla dium(0) were placed in the glass linerof a rotating autoclave which was sealed and heated to a temperature ofl 15C. The autoclave was allowed to remain at this temperature of ll5C.for a period of 7 hours. At the end of this time, heating wasdiscontinued, the autoclave was allowed to return to room temperatureand the reaction mixture was recovered.

Analyses, by means of a gas liquidchromatograph, of the mixture disclosethe presence of 69 percent of the 2,7-dimethyll ,3,7-octatriene withonly 27.4 percent of the 2,6 -dimethyl-l,3,7-octatriene, 0.4 percent ofthe 3,6-dimethyl-l,3,7-octatriene and 3.2 percent of other C isomers.

EXAMPLE II EXAMPLE III In this example 109 g. (0.75 mol) of myrcene (2methyl-6-autoclave which contains 1.25 g. (0.0009 mol) oftetrakis(tritolylphosphite)palladium(0). The autoclave is sealed andnitrogen is pressed in until an initial pressure of 30 atmospheres isreached. The autoclave is then heated to a temperature of C. and

maintained thereat for a period of 8 hours. At the end of this 8 hourperiod, heating is discontinued, the autoclave is allowed to return toroom temperature, the excess pressure is discharged and the autoclave isopened. The reaction mixture is recovered, separated from the catalystby filtration and analyzed by means of a gas liquid chromotograph. Thisanalysis will disclose the presence of the selective dimer which is 2,15dimethyl-6,l 1-dimethylene-2,7,l4-hexadecatriene.

I claim as my invention:

1. A process for the selective dimerization of a conjugated diolefinichydrocarbon which comprises treating said hydrocarbon at dimerizationconditions including a temperature of from about 25 to about 250 C. anda pressure of from about atmospheric to about 100 atmospheres in thepresence of an organopalladium complex selected from the groupconsisting of tetrakis (triphenylphosphite)tetrakis(tribenzylphosphite)palladium(),tetrakis(tritolylphosphite)palladium(0),tetrakis(triethylbenzylphosphite)palladium(0)tetrakis(trixylylphosphite)-palladium(0).

and

palladium(0),

2. The process of claim 1 in which said conjugated diolefinichydrocarbon is isoprene.

3. The process as set forth in claim 1 in which said organopalladiumcomplex is tetrakis(triphenylphosphite)palladium(0).

4. The process as set forth in claim 1 in which said organopalladiumcomplex is tetrakis(tribenzylphosphite)palladium(0).

5. The process as set forth in claim 1 in which said organopalladiumcomplex is tetrakis(tritolylphosphite)palladium(0).

6. The process as set forth in claim 3 in which said conjugateddiolefinic hydrocarbon is 2-methyl-l,3-butadiene.

7. The process as set forth in claim 3 in which said conjugateddiolefinic hydrocarbon is l ,3-butadiene.

8. The process as set forth in claim 3 in which said conjugateddiolefinic hydrocarbon is 2-methyl-6- methylene--2,7-octadiene.

9. The process of claim 3 in which said conjugated diolefinichydrocarbon is isoprene.

2. The process of claim 1 in which said conjugated diolefinichydrocarbon is isoprene.
 3. The process as set forth in claim 1 in whichsaid organopalladium complex istetrakis(triphenylphosphite)palladium(0).
 4. The process as set forth inclaim 1 in which said organopalladium complex istetrakis(tribenzylphosphite)palladium(0).
 5. The process as set forth inclaim 1 in which Said organopalladium complex istetrakis(tritolylphosphite)palladium(0).
 6. The process as set forth inclaim 3 in which said conjugated diolefinic hydrocarbon is2-methyl-1,3-butadiene.
 7. The process as set forth in claim 3 in whichsaid conjugated diolefinic hydrocarbon is 1,3-butadiene.
 8. The processas set forth in claim 3 in which said conjugated diolefinic hydrocarbonis 2-methyl-6-methylene-2,7-octadiene.
 9. The process of claim 3 inwhich said conjugated diolefinic hydrocarbon is isoprene.